Compressing machine



June 18, 1935.. 7w D. D E 2,005,578

,QOMPRESSING MACHINE Filed Aug. 6, 1932 5 Sheets-Sheet l June 18, 1935.w. D. DRYSDALE COMPRESSING MACHINE Filed Aug. 6, 1952 5 Sheets-Sheet 2flzlysdaze,

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Patented June 18, 1935 UNITED STATES, PATIENT." OFFICE COMPRESSINGMACHINE William D. Drysdale, Buflalo, N. Y., assignor to Walter J.Sugden, Boston,jMass.

Application August 6, 1932, Serial No. 627,736

I 19 Claims. This invention relates to a compressing machine susceptibleof general application, but partioularly useful in connection withmechanical refrigerators, of the compressor, condenser, expander type,and more particularly to a. machine comprising a compressor driven by anelectric motor. This invention aims to provide a machine of this classwith a direct driving mechanism without a reduction or other ratiobetween the driving and driven members, and having means whichshalleither partially or wholly avoid creating a load on the motor during thestarting of the latter, thereby enabling a motor of low starting torqueto be employed, without resort to the use of a belt drive, or othermeans of establishing a ratio permitting the motor shaft to operate athigher speeds than the apparatus it drives through the belt, or acapacitor motor,

to allow the motor to take up the load of the compressor gradually. Theinvention also aims to p1 ovide a driving mechanism which shall causethe piston of the compressor to maintain the compressor intake closedwhen the compressor is at rest, thereby preventing therefrigerant fromflowing into the compressor cylinder.

The invention will best be understood by reference to the followingdescription, when taken in connection with the accompanying drawings ofone specific embodiment thereof, while its scope will be pointed outmore particularly in the appended claims.

In the drawings: Fig. l is a plan of a motor-driven compressor embodyingthe invention;

Fig. 2 is a vertical, longitudinal section, on an enlarged scale, online 2-2 of Fig. 1;

Figs. 3, 4, 5 and 6, are sectional views, on an enlarged scale, on line33 of Fig. 1, illustrating the operation of the unloading mechanism;

Fig. 7 an end elevation of the unloading mechanism in its neutral orinitial position;

Fig. 8 is a sectional view on line 8-8 of Fig. 2; Fig. 9 is ahorizontal, sectional view on line 9-9 of Fig. 3; 1 Fig 10 is ahorizontal, sectional view illustrating the inlet for the refrigerantinto the motor housing; I r

Fig. 11 is a sectional view illustrating one of the electric terminalsfor the motor;

Figs. 12 and 13 are end elevations of the unloading mechanismillustrating a slight modification, inwhich the load of the compressoris entirely removed from the motor for starting purpo e 3 Figs. 14-and15 aresectional views corresponding with Figs. 12 and 13, respectively,and illustrating the means for predetermining the limits of movement ofthe oscillatory elements of the unloading mechanism; and

Fig. 16 is a sectional view similar to a portion of Fig. 2, showing aslight modification.

Referring to the drawings, and to the embodiment of the inventionillustrated therein, and having reference at first more particularly toFig. 3, there is shown a motor-driven compressor, the latter comprisinga cylinder 20 having a lateral intake port 2|, which is covered anduncovered 1 by a piston 22.

through openings 23 in a plate 24, having an annular seat 25 for anoutlet valve 26, which, as shown, is a thin, steel, wafer-like disk,normally urged to its seat by a spring 21 within an outlet chamber 23formed in a cylinder head 29, and communicating with an outlet passage33, the latter in practice being connected with a condenser. In thepresent example, the cylinder 20 is in the nature of a sleeve or lining,fixedly mounted in a surrounding support, herein a housing 3i, having achamber 32 which encloses part of the driving mechanism.

The driving'mechanism, as herein shown, comprises an element such as acrank-pin 33, having an orbital path, and suitably connected to thepiston to reciprocate the latter, the connection shown being a shoe orcross-head 34, mounted to slide in a groove extending transversely ofthe piston, though the invention is not limited to this form of drivingconnection, but might employ a connecting rod.

The charge drawn into the cylinder and compressed by the piston isdischarged Turning now to Fig. 2, the crank-pin is driven by a rotatableelement, herein a shaft 36, mounted to rotate in a bearing 31 presentedby a plate 38, which constitutes a cover for the chamber 32. The plate38 constitutes a partition between the r chamber 32 and a motor chamber39 also formed in the housing 3|, and the other end of this motorchamber is closed and sealed'by a cover-plate 40, thus providing asealed housing for the entire mechanism.

The'motor chamber 39 houses an electric motor comprising a stator 4!fixed in the housing,

and a rotor l2 suitably secured to theshaft 36, as

by providing the latter with a reduced portion 43, to which the rotor issecured, as by a key 44 and by a nut 45 threaded onto a further reducedportion 46. The nut urges the rotor, and a suitable thrust washer 61toward a shoulder 48 presentedby the body oithe shaft, said washerresting against the adjacent endof' the-bearing 31.

The rotor is slightly offset axially with relation to the stator in a.direction opposite to the bearing, thereby to utilize the magnetic fluxto eliminate any tendency of the rotor to move endwise. The stator hasthree-lead wires 49, attached respectively to lead-in plugs 50, one ofwhich is shown in detail in Fig. 11, the same comprising a conductor 5|for attachment to the wire, and a tapered, threaded, insulating shell52, which is screwed into the housing 3|. The details of this plug haveno necessary bearing upon the present invention, and therefore requireno further description.

Referring now to Fig. 10, in the embodiment shown, the refrigerant to becompressed. instead of entering the chamber 32 directly, enters themotor chamber 39, as by 'means of a plug 58 threaded into the housing,and provided with passages 54 and 55, the former being connected asusual with an expander. The refrigerant, after entering the motorchamber 39, enters the lower end of a conduit 56 (see Fig. 2), andpasses thence through passages 51 and 58 in the plate 33 into thechamber 32. From this chamber, the gas passes upwardly through a passage59 in the housing 3| (see Fig. 3, and thence through a port 60 inregistration with the lateral intake port 2| of the cylinder 28. Thus,the refrigerant on its way to the cylinder, passes through the motorchamber, and cools the motor, as well as the shaft and its bearing.

The unloading mechanism'will now be described, reference being had atfirst to Fig. 2. In

general, the mechanism imparts to the piston a reciprocatory motion ofvariable amplitude, varying from'a zone in which the piston covers anduncovers the lateral intake port and causes gas to be admitted throughsaid port and discharged past the outlet valve toa zone within which thepiston maintains said port closed. In the first zone, a full stroke isimparted to the piston, while in the second zone, the stroke is eitherreduced to one of small amplitude, or if desired may be reduced to zero.In' the form shown in Figs. 2 to 8, inclusive, the stroke is reduced toone of small amplitude, while in the form shown in Figs. 12 to 15,inclusive, the stroke is. reduced to zero. The amount of reduction ofthe stroke is determined by the amount of eccentricity of theoscillatory element now to be described.

Referring to Fig. 2, the crank-pin which has been referred to as anelement having an orbital path is carried by an oscillatory element,herein a rockshaft 6|, having an axisof. oscillation eccentric to theaxis of rotation of the rotatable element, namely, the shaft 36. When,therefore, the rockshaft 6| is turned about its axis, the radius of theorbit of the crank-pin is varied from a radius in which the piston iseffective to cover and uncover the lateral intake port of the cylinderto a radius in which the piston is ineffecthe motor to start tive touncover said port, and, furthermore, this change of radius changes theload of the compressoron the motor from full load, in which the pistonis at full stroke, to a reduced load or no load at all, depending, ashas been stated, upon the of the rockshaft. This reduction, or totalelimination of the load, enables and to get up to speed partially orwholly free from load, and therefore a motor of low starting torque canbe employed, with a direct drive, instead of using otherexpedientsheretofore employed.

. As herein shown, the eccentricity of the rockshaft SI andcorresponding eccentricity of the .Fig. 8), having a reduced portion 64,which is received in asegmental groove 65 in the rockshaft. If desired,the screw and the slot may be located near the inner end of therockshaft, as shown in Fig. 16. The screw and slot, while employedprimarily to prevent endwise movement of the rockshaft, also serve asone means to limit turning movement offthe rockshaft. However, as theyare near the axis, I prefer to employ other stops presently to bedescribed, much farther from the axis, to limit turning movement of therockshaft. I

While the weight 62 might be relied upon without other aid to controlthe turning of the rockshaft, under the influence of variations in thespeed of the motor, I prefer to employ a spring 66 (see Fig. 2) toassist the weight.- This spring can be arranged to present a yieldingresistance tothe weight 62 in either direction,- that is to say, it maybe utilized either to increase orto decrease the, eccentricity of thecrank-pin; but in the embodiment shown, the

spring is arranged to have a neutral position in which it is notstressed, and in which position the stop screw 63 (see Fig. 8) is in thecenter of the segmental slot 65 when the machine is at rest, the intakeport being closed. This is simply a matter of securing the ends of thespring in the desired relationship to the parts which they connect. Asshown in Fig. 2, one end of the spring is wound about and secured to aplug 61, having a tongue 68 which is received in a slot 69 in the shaft36, and; the other end of the spring is wound about and securedtoasimiiar plug 10, having a tongue ll received in a slot 12 in therockshaft 6|. As herein shown, these slots are conveniently formed bymaking drilled holes, into which the tongues extend laterally.

In order that the rotating parts shall be in balance after the fullspeed of the motor is attained, I provide the rotatable shaft 36 with afly-wheel 13, having a weight 14, which is opposite to the weight 62when the latter is fully advanced. The counterweight 14 balances theweight 62, as well as the rockshaft with its crankpin. This ensuressmooth running, without noticeable vibration, as the two weights underthis condition constitute together a balanced flywheel. The fly-wheel I3is provided with stops l6 and 11 (see Fig. 7), to be engaged by oppositeedges of the weight 62 to limit turning movement of the rockshaft 6! inopposite directions.

The operation of the unloading mechanism will readily be understood froma comparison of Figs. 3 to 8, inclusive. Fig. 3 shows what may be termedtheretarded position, in which .the radius of the crank-pin is atminimum and the stroke of the piston is correspondingly at minimum. Asherein'before stated, in the initial position of the crank-pin, whenparts are at rest, the crank-pin may have a slight throw, as shown inFigs. 3 to 8, inclusive, or its axis may be coincident with the axis ofthe rotatable shaft 36, in which it has no throw at all, as shown intheform illustrated in Figs. 12 to 15, inclusive. The form illustratedin Figs. 3

to 8, inclusive, is preferred, because of the small'- er radius throughwhich the crank-pin and the rqckshaft turn in advancing and retarding.This short radius gives the eccentric weight an inin the compressionchamber.

creased leverage in throwing the crank-pin to its position of maximumthrow, and in maintaining the piston at full stroke, and hence atmaximum pumping eficiency. When the piston is in its maximum operatingposition, that is at the full stroke, the main shaft, rockshaft' andcrank-pin centers are preferably directly over each other in the ordernamed. This pro-. vides a positive drive, so that the piston operatesjust as efficiently in this position as if no starting relief wereprovided. Furthermore, as hereinafter suggested, until this full strokeof the piston is reached, the piston may fall back and cushion anyexcess burden imposed by oil slugs When the'rockshaft is in its neutralposition and when the machine is at rest, the lateral intake port. 2| iscovered by the piston 22, and no refrigerant can enter the cylinder.When the port is closed, the refrigerant in the cylinder is simplycompressed slightly, and then expanded, thus imposing no material loadupon the motor. When the motor starts, there is only a slight load, ornone at all, depending of course upon the amount of eccentricity of therockshaft 6|. With the first form, the stroke of the piston, when themotor starts to run, is shown by a comparison of Figs. 3 and 4, Fig. 3showing the piston at the bottom of its stroke, and Fig. 4 showing thepiston at the top of its stroke.

As the speed of the motor increases, the eccentricity of the crank-pinincreases, until in the 'full running position shown in Figs. 5 and 6,

the piston has its maximum stroke, Fig. 5 showing the piston at thebottom of 1 its stroke with the port 2| uncovered by the piston, andFig. 6 showing the piston at the top of its stroke with a slightclearance, amounting in practice to a few thousandths of an inch. Duringthe increase of the piston stroke and before the full stroke is reached,if an oil slug should happen to be taken into the cylinder, no damagewill result, because the resistance which is encountered will naturallycause ,a slight retardation in the position of the crank-pin, and acorresponding momentary shortening of the stroke of the piston.

It might be supposed that it would be more desirable to have the settingof the spring 66 such that the latter would tend toretain the crankpin33 in its fully retarded position,-that is, in the position in which thecrank-pin'has its shortestthrow; Such setting of the spring has beenfound to produce satisfactory results, but it has been found moredesirable to set the spring so that it tends to restore the-crankin toits mid position. With the latter. setting of the spring, the crankpinis at mean position when l the machine is at rest and the intakeport' isclosed,

. When'the motor starts, the weight 62 will by its inertia lag behindthe shaft 36, and will thus bring the crank-pin momentarily to itsminimum throw, in opposition tothe resistance of the spring. When,however, the shaft acquires sufiicient speed, the centrifugal effect ofthe weight, due to its eccentric mounting, results in the weight beingthrown outwardly with relation to the shaft. During the first half ofthis movement,the spring. which is under stress assists the weight inmoving-outwardy with relation to the shaft.

Asthespeedof the shaft increases, the weight carries the rdckshaftandthe crank-pin past the neutral position of the spring, and thereafterthe spring is stressed in the opposite direction, and yieldingly resistsoutwardmovement of the weight. When the weight, the rockshaft and thecrank-pin reach their extreme outward position, the crank-pin has itsgreatest throwand the piston its greatest stroke. a

When the current is cut off from the motor, and the speed of the shaftis reduced, the weight commences to lag-behind the shaft, and isassisted by the spring during the first half of this backward movementwith relation to theshaft. During this time, the throw of the crank-pinis reduced, the stroke of the piston is correspondingly decreased andthe load on the motor is diminished, inasmuch as the piston has littleor no work to do, depending of course upon whether the design shown inFigs. 3 to 8, inclusive, or that which is shown in Figs. 12 to 15,inclusive, is used. Moreover, it is to be noted that only a very slightshortening of the stroke of the piston is required to prevent the latterfrom uncovering the intake port. This means a definite and quick reliefof compression stresses and consequent load on the motor.

Observation of the operation of the design illustrated in Figs. 3 to 8,inclusive, shows that sometimes when the motor stops, the crank-pin hasreturned to its position of minimum throw in opposition to the spring,while at other times, it returnsonly to the mid position in which thespring is neutra1,-that is, not under stressf Observation has also shownthat if the machine stops with the crank-pin at mid throw, when themotor starts again, the lag of the weight will bring the crank-pinmomentarily to its minimum throw, and then as the speed of'the motorincreases, the crank-pin throw will be increased'to maximum, as themotor speed approaches or reaches maximum.

Having thus described one embodiment of the invention, but withoutlimiting myself thereto,

outlet valve, to a zone within which said piston maintains said portclosed.

2.- In a refrigerant pump, the combination of a cylinder having alateral intake port, an outlet valve, a piston working insaid cylinderand adapted to cover and uncover said port, means to reciprocate saidpiston, said means including an element having an orbital path, 'andmeans to change the path of said element to vary the stroke of saidpiston from a full stroke during which said piston covers and uncoverssaidport to a condition during which said piston maintains said portcovered.

3. In a-refrigerant pump, the combination of a cylinder having a lateralintake port, an outlet valve, a piston working in said cylinderandadapted to cover and uncover said port, means to reciprocate saidpiston, said means including an element having an orbital path, andmeans to vary the radius of the orbit of said element from a radius inwhich said piston is effective to cover and uncover said port to aradiusin which said piston is ineffective to uncover said port.

4. In a refrigerant pump, the combination of a cylinder having a lateralintake pcrt, an outlet -valve, a piston working in said cylinder and'first-mentioned element from a path in which the latter is effective tocause said piston to cover and uncover said port to a path in which thefirstmentioned element is ineffective to cause said piston to uncoversaid port.

5. In a refrigerant pump, the combination of a cylinder having alateralintake port, an outlet valve, a piston working in said cylinder andadapted to cover and uncover said port, a rotatable element, anoscillatory element carried by said rotatable element and having an axisof oscillation eccentric to the axis of rotation of said rotatableelement, an orbitally movable element carried by said oscillatoryelement inan orbital path during the rotation of said rotatable element,and means to cause said oscillatory element to oscillate about its axisto shift said orbitallymovable element toward and from the axisrotatable element, an orbitally movable element of aaid rotatableelement.

6. In a refrigerant pump, the combination of a cylinder having a lateralintake port, an outlet valve, a piston working in said cylinder andadapted to cover and uncover saidport, a rotatable element, anoscillatory element carried by said rotatable element and having an axisof oscillation eccentric to the axis of rotation of said rotatableelement, an orbitally movable ele ment carried by said oscillatoryelement in an orbital path during the rotation of said rotatableelement, biasing means normally to retain said oscillatory elementin aninitial position adapted to yield to permit said oscillatory element tomove about its axis, and means to cause said oscillatory element to movein opposition to said biasing means.

7. In a refrigerant pump, the combination of a cylinder having a lateralintake port, an outlet valve, a piston working in said cylinder andadapted to cover and uncover said port, a rotatable element, anoscillatory element carried by said rotatable element and having an axisof oscillation eccentric to the axis of rotation of said rotatableelement, an orbitally movable element carried by said oscillatoryelement in an orbital path during the rotation of said rotatableelement, biasing meansnormally to retain said oscillatory element in aninitial position and adapted to yield to permit said oscillatoryelementto move about its axis, and speed-responsive means to cause saidoscillatory element to move in opposition to said biasing means.

8. In a refrigerant pump, the co i'nbination of a cylinder having alateral intake port, an outlet valve, a piston working in said cylinderand adapted to cover and uncover said port, a rotatable element, anoscillatory element carried by said rotatable element and having an axisof oscillation eccentric to the axis of rotation of said rotatableelement, an orbitally movable element carried by said oscillatoryelement in an orbital Path during the rotation ofsaid rotatable element,means to limit the oscillatory movement of said oscillatory element, andspeed-responsive means to cause said oscillatory element to oscillate inaccordance with variations in the speed of rotation of said rotatableelement.

9. In a refrigerant pump, the combination of a cylinder having a lateralintake port, an outlet valve, a piston working in said cylinder andadapted to coverand uncover said port, a rotatable element, anoscillatory element carried by said rotatable element and having an axisof oscillation eccentric to the axis of rotation of said rotatableelement, an orbitally movable element carried by said oscillatoryelement in an orbital path during the rotation of said rotatableelement, means to limit the oscillatory movement of said oscillatoryelement, speed-responsive means to cause said oscillatory element tooscillate in accordance with variations in the speed of rotation of saidrotatable element, and a spring which resists oscillatory movement ofsaid oscillatory element and restores said oscillatoryel-ement to itsinitial position as the speed of rotation of said rotatable element isreduced.

10. In a refrigerant pump, the combination of a cylinder havinga lateralintake port, an outlet valve, a piston working in said cylinder andadapted to cover and uncover said port, a rotatable element, anoscillatory element carried by said rotatable element and having an axisof oscillation eccentric to the axis of rotation of said of saidrotatable element, and a spring which resists oscillatory movement ofsaid oscillatory element and tends to restore said oscillatory elementto an initial position between said limits as the speed of rotation ofsaid rotatable element is reduced.

11. In a refrigerant pump, the combination of a cylinder having alateral intake port, an outlet valve, a piston working in said cylinderand adapted to cover and uncover said port, a rotatable element, anoscillatory element carried by said rotatable element and having an axisof oscillation eccentric to the axis of rotation of said rotatableelement, an orbitally movable element carried by said oscillatoryelement in an orbital path during the rotation of said rotatableelement, a weight carried by said oscillatory element to cause thelatter to oscillate about its axis in response to variations in thespeed of said rotatable element to shift said orbitally movable elementtoward and from the axis of said rotatable element, and a weight carriedby said rotatable element to counterbalance the first-mentioned weightwhen said orbitally movable element is at its greatest distance from theaxis of said rotatable element.

12. In a refrigerating machine, the combination of a compressor tocompress the refrigerant, said compressor including a cylinder having alateral intake port, a piston reciprocating in said cylinder andcovering and uncovering said port, a motor to drive said compressor, anddriving mechanism connecting said motor and said compressor, andcomprising means responsive to the speed of said motor to vary theamplitude of the stroke of said piston from a zone in which the pistoncovers and uncovers said port to a zone in which said piston maintainssaid port closed.

13. In a refrigerating machine, the combination of a compressor tocompress the refrigerant, a rotatable element to drive said compressor,and positive driving mechanism connecting said element to saidcompressor, said driving mechanism including a revoluble element whichis revoluble about an axis other than its own, and means responsive tovariations of the speed of said rotatable revoluble element to move saidelement toward the axis of said rotatable element when the speed of saidrotatable element is reduced, and to move said revoluble element fromthe axis of said rotatable element when the speed of said rotatableelement is increased.

14. In a refrigerating machine, the combination of a compressor tocompress the refrigerant, a rotatable element to drive said compressor,and positive driving mechanism connecting said element to saidcompressor, said driving mechanism includin a crank-pin which drivessaid compressor, and means responsive to variations of the speed of saidrotatable element to move said crank-pin toward the axis of saidrotatable element when the speed of said rotatable element is reduced,and to move said crank-pin from the axis of said rotatable element whenthe speed of said rotatable element is increased.

15. In a refrigerating machine, the combination of a compressor tocompress the refrigerant,said compressor including a cylinder and apiston to reciprocate therein, a rotatable element to drive said piston,and driving mechanism between said element and said piston, said drivingmechanism including stroke-changing means responsive to changes of thespeed of said element to diminish the length of the stroke of saidpiston as the speed of said rotatable element diminishes, and toincrease the length of said stroke as the speed of said rotatableelement increases.

16. In a refrigerating machine, the combination of a compressortocompress the refrigerant, a shaft to operate said compressor, anddriving mechanism connecting said shaft and said compressor, saidmechanism including a crank-pin, and means responsive to the speed ofsaid shaft to move said crank-pin toward the axis about which itrevolves when the speed of said shaft diminishes, and to move saidcrank-pin from said axis as the speed of said shaft increases.

17. In a refrigerating machine, the combination of a compressor tocompress the refrigerant, an electric motor, and driving mechanism atall times connecting said motor to said compressor, said mechanismincluding means to increase the mechanical advantage as the speed ofsaid motor diminishes and to decrease the mechanical advantage as thespeedof said motor increases, said means including a weight which tendsto lag behind said motor when said motor starts, and to lag behind saidmotor when the speed of said motor diminishes.

13. In a refrigerating machine, the combination of a compressor tocompress the refrigerant, an electric motor, and driving mechanism atall times connecting said motor to said compressor, said mechanismincluding means automatically to change the driving relationship betweensaid motor and said compressor in accordance with differences betweenthe power of said motor and the load of said compressor, said meansincluding a weight which causes the eifective load to be at minimum whenthe power of said motor is at minimum, and which causes the effectiveload to be at maximum when the power of said motor is at maximum.

19. In a refrigerating machine, the combination of a compressor tocompress the refrigerant, an electric motor, and gearlessspeed-responsive mechanism at all times connecting said motor and saidcompressor to increase the mechanical advantage asthe speed and torqueof said motor' diminish and to decrease the mechanical advantage as thespeed and torque of said motor increase.

M D. DRYSDAIE.

